1. Field of the Invention
The present invention relates to a method and apparatus for piling plural sheets of material having a repetitive pattern thereon, while ensuring the vertical alignment of the patterns from one sheet to the next.
The manufacture of articles formed by a juxtaposition of several pieces cut out from sheets of patterned material generally raises some difficulties whenever it is required to match the patterns together along the assembly process. This can be the case in the tailoring industry, for example, whenever clothes are made from material having a repetitive pattern. The same problems can also occur in other fields of industry, such as: vehicle manufacturing (upholstery of car seats), furniture making and, more generally, all industries which call upon the assembly of pieces made of soft material, such as cloth, while having to maintain correct registration of the patterns.
For instance, when making an item of clothing from a patterned material, it is necessary to determine accurately the places where the patterns are to match. It will here be assumed that the dress pattern was defined at an ealier stage and that the operator possesses the corresponding templates and knows exactly the model to be produced from the work of the stylists and designers. This matching will generally be required whenever it is desired to provide continuity to the pattern while creating a three-dimensional configuration. These places are specifically marked out on the templates. The operator accordingly spreads out a ply of cloth over the table and begins to dispose the templates directly above the ply, making sure that the appropriate markers on the template coincide with the patterns on the cloth. Once this operation is completed, the operator has a layout according to which the different pieces can be cut out. He or she then proceeds to assemble the pieces together until is obtained the garment in its final form. The above procedure, while described above as a totally manual process, can of course be improved by employing known and commonly used devices for automatically grading dress patterns, cutting them out and recording the position of the templates on the cloth.
2. Prior Art
In this type of manufacturing process, the cutting out sequences are reptititive and the same operations must be re-iterated for each new ply of material. While this is perfectly acceptable for "made-to-measure" tailoring where dimensions constantly change from one garment to another, it is however inefficient when dealing with small or medium scale production runs. It is more appropriate, in the latter case, to cut out several plies at once. A number of known techniques are available for this. They are all manual and employ traditional pin tables. The operator must superimpose several plies of cloth while accurately aligning the pattern of one ply above the other. This is achieved by using pins that fix the joining points of the pattern. The pins are arranged vertically and directly on the cutting table. Depending on the working method adopted, the pins can be placed either along a master trace, or according to a standard "grid" closely matching that of the pattern. The pins are always placed before laying down the first ply of material. The operator then lays down the plies successively, pushing the pins one-by-one through each individual ply at the correct places. Since the pins are fixed, some stretching or pulling-in of material will be necessary to bring it to the required position. Although the patterns are repetitive, they never have exactly the same repetition pitch, which explains the necessity for these constant readjustments. Once the pile has been completed, the resulting wad is cut out directly on the table, after the operator has removed the pins. This is the only procedure that gives satisfactory results. However, it is completely manual, lengthy and tedious, as well as impractical and incompatible with automatic cutting machines.